Hearing aid casing of the miniature type



March 8, 1966 GATH HEARING AID CASING OF THE MINIATURE TYPE 2 Sheets-Sheet 1 Filed Oct. 20. 1961 IN VEN TOR. TONY GATH BY 4 5 f A TTORNE Y3 March 8, 1966 T. GATH HEARING AID CASING OF THE MINIATURE TYPE 2 Sheets-Sheet 2 Filed Oct. 20. 1961 IN VEN TOR. TONY GATH BY M A TTORNE Y5 United States Patent 3,239,093 HEARING AID CASING OF THE MINIATURE TYPE 7 Tony Gath, Heriev, Denmark, assignor to American Danish ()ticon A/S (Akts. William Demant), a corporation of Denmark Filed Oct. 20, 1961, Ser. No. 146,570 Claims priority, application Great Britain, Oct. 24, 1960, 36,411/60 6 Claims. (Cl. 2204) The present invention relates to hearing aid apparatuses of the miniature type comprising a plurality of electronic miniature components enclosed in a plastic casing.

The term miniature hearing aid apparatus as used here and in the following shall be construed to include unitary self contained hearing aid apparatuses of small dimensions as well as hearing aid apparatuses included in other items, such as for example in hearing aid spectacles.

It is a purpose of the invention to provide an apparatus of the type referred to in which the casing easily can be assembled from two parts which can be easily disassembled for the purpose of service and/ or repair.

It is a further purpose of the invention to provide an apparatus of the type referred to in which the casing easily can be assembled by means of assembling means associated with the two parts of the casing.

It is a further purpose of the invention to provide a miniature hearing aid apparatus in which the casing can be assembled from two parts without use of screws or adhesive.

Still a further purpose of the invention is to provide a hearing aid apparatus of the miniature type in which the casing can be assembled from two parts without the use of tools.

Still a further purpose of the invention is to provide a miniature hearing aid apparatus in which the casing is assembled by locking engagement between locking members of each of the two parts of the casing which will hold the casing safely assembled, and still enable the casing to be disassembled for the purpose of service and repair without the risk of damaging the casing.

Further purposes of the invention will appear from the following specification in connection with the description of the accompanying drawing, in which FIGURE 1 is a perspective view of a casing of a miniature hearing aid apparatus according to the invention,

FIGURE 2 is a perspective view in enlarged scale of one of the two parts of the casing,

FIGURE 3 is a perspective view in similarity with FIGURE 2 showing the other part of the casing,

FIGURE 4 is a perspective view of the part of the casing shown in FIGURE 2, illustrating the arrangement of the electronic components within the casing,

FIGURE 5 is a section through the casing showing a cross section of the lock means on an enlarged scale, and

FIGURE 6 is a cross section through the lock means showing a modified embodiment thereof.

The hearing aid apparatus as illustrated in FIGURES 15 is of the miniature type comprising a plurality of electronic miniature components which are enclosed in a casing 10. The casing 10 is assembled from two half parts 12 and 14 of plastic material which are substantially of similar size and configuration and which are assembled in edge to edge relationship along a line which in FIGURE 1 is referred to as 16.

The assembly is effectuated by means of'lock projec tions 18 at the edge of the half part 12 being integral with the wall structure of the casing in locking engagement "with lock recesses 2i) at the edge of the other casing part "ice 14. In order to provide for locking engagement between the projecting lock means 18 and the locking notches 20 a plastic material is selected for the manufacture of the two half portions of the casing which is characterized by being relatively stiff but elastically deformable with its elasticity so adapted to the dimensions of the extension of the projecting lock means 18 and the depth of the lock recesses 20 in a plane through the assembly line 16 so as to enable the two parts of the edge zones at least of the wall structure defining the casing half parts to be elastically deformed to provide for the locking engagement as well as disengagement.

I have found that surprisingly it is possible only by such simple locking means to obtain an assembly of the two parts of the casing which enables the two parts to be clicked together without the danger of damaging the lock means and that in addition a locking engagement is obtained which requires more force to separate the two parts of the casing when they are assembled than required for clicking them together.

In addition to these surprising merits, of the assembly the invention results in a plurality of advantages with respect to the production of this specific type of hearing aid apparatus as well as advantages for the user.

An assembly of parts with such small dimensions as used for miniature hearing aid apparatuses by means of screws is inconvenient for many reasons. It requires screws of very small dimensions with so time screw threads that in production it must be considered as nearly impossible to provide corresponding screw-threaded holes in the plastic material. Therefore miniature screwthreaded bushing would have to be molded in the plastic which also causes substantial difliculties in production. Also bonding of the casing parts together is inconvenient. The adhesive must be applied only at the edges with the utmost care, and even in this event it is unavoidable that when the casing portions are assembled adhesive enters the cavity and comes into contact with some of the components. This can cause damaging of the apparatus, for example by causing stifliening of sponge material which may be included between the casing wall and the microphone or sound reproducer of the apparatus. In addition, in production, the final test of correct function of the electronic circuits cannot be carried out until after the apparatus is assembled, and when defects are found during the final test inside a casing which is bonded together it is nearly impossible to separate the casing parts again without damaging the casing, and the result is a substantial reject of casings in the production. Also with respect to servicing the casing having two bonded parts is inconvenient because if the casing can be separated for the purpose of servicing the exterior finish will not be the same after reassembly and the reassembly with bonding material after servicing involve-s the same risk of adhesive entering the cavity as in production.

Eventually, assembly by screws or by adhesive is a time-consuming procedure in the production as well as in servicing with the result that the wearer of the hearing aid in the case of servicing must be without his apparatus for a certain time.

The invention provides, however, for lock means integral with the casing wall structure. The lock means is provided in the mould for moulding the two half parts of the casing. All time-consuming assembly operations are avoided and the two half parts of the casing can be clicked together by a simple operation which is a matter of one or two seconds. cuits or components inside the casing are found after the assembly it is also a simple operation which is a matter of one or two seconds to separate the parts of the casing without the risk of damaging the parts whereby If defects in the electronic cirin production reject of casings is avoided completely. The same counts for servicing which can be carried out much quicker and easier than previously which of course is of great advantage for the user of the apparatus.

The apparatus shown in FIGURES 1-4 is a miniature of the apparatus adapted to be carried behind the ear, and the casing is an elongated peanut-like casing having a concave side and a convex side. The length of the casing may be about 1 /2 inch and the width of about /2 inch or slightly more.

The casing half portion 12 is provided with bottom ribs 22 and 24 which operate as stiffening ribs and define a compartment for positioning a sound reproducer 26 inside the casing. The sound reproducer has an outlet which through a plastic pipe is connected to a nipple 28 which is secured in a hole in the narrow end of the casing and which is designed for connection with an ear piece (not shown). On each side of an aperture 30 through which a manually actuating member 32 of a volume control extends inwardly extending guide ribs 34 and 36 are provided for engaging on either side of the volume control and positioning it inside the casing.

Adjacent the other end of the casing inwardly extending pairs of ribs 40 and 42 respectively are provided on either side of an aperture 38 which communicates with a compartment adapted to receive a dry cell or the like for energizing the electronic apparatus. The pair of ribs 40 defines adjacent the right hand end of the casing a compartment which is adapted to receive the microphone which has a fin or rib engaging between the pair of ribs 40 so as to be positioned by engagement therewith. An air intake 44 is provided at the right hand end of the casing to enable the sound waves to reach the microphone. The other pair of ribs 42 is designed to position a switch 46 by engagement of a member associated therewith. A manual control member 48 for the switch extends through. a slot 50 in the casing wall. A pair of ribs 52 defines together with the rib 36 a compartment in the middle portion of the casing in which the electronic amplification part is positioned. This part includes a complete amplifier constructed by means of miniature components including transistors, resistors, condensers, etc. To close the aperture 38 to the dry cell compartment a removable cover (not shown) is provided.

In the casing portion 14 shown in FIGURE 3 ribs and partitions 22a, 34a and 36a are provided corresponding to the ribs and partitions 22, 34 and 36 in the casing portion 12. In the right hand end of the casing portion 14 only two partitions 40a and 42:: are provided on each side of the battery compartment.

In the embodiment illustrated the lock projections on the casing portion 12 are in the form of ribs integral with the wall structure which defines the casing. Said lock ribs extend along a substantial part of the assembly edge of the casing portion 12. One rib section 18a extends from adjacent the narrow end of the casing to the aperture 30. Between this aperture and the aperture 38 a second rib portion 18b extends. A third rib portion 180 extends from the other side of the aperture 38 to the rib or partition 52 which limits the right and side of the amplifier compartment. On the other side of this compartment a further rib portion 18d extends to adjacent the narrow end of the casing.

In a corresponding manner the casing portion 14 has outwardly facing lock notch sections 2911-2042, the length of which corresponds to the length of the lock rib sections. 1,

In the embodiment shown the projecting lock means or lock ribs are provided with inwardly facing inclined surfaces 18' and the lock recesses or grooves are provide-d with corresponding outwardly facing inclined surfaces 20, see FIGURE 5. The inclined surfaces 18' and 20' form an acute angle with a line perpendicular to the plane through the assembly line of the two casing halves. This angle is the same on the projection or rib where it is in engagement with the recess 0r groove. In order to secure easy clicking of the two casing portions together without the risk of damaging the edges of the lock projections the angle must not be too large and is preferably below 20. I have found it convenient that the angle of the inclination is different at edge portions which are substantially linear or only slightly curved and at portions where the wall is bent sharply or having a small radius of curvature. In the case of a peanut shaped casing as shown the angle of inclination may adjacent the middle of the casing be between 7 and 10 and at the corners where the radius of curvature is smaller the angle may be between 3 and 5 which I have found results in an easy locking engagement with a very firm grip.

With the dimensions of the casing referred to hereinbefore the height of the lock ribs 18 perpendicular to a plane through the assembly line may be between and inch. With an angle of inclination of 7 of the inwardly facing surface of the rib 18 the top edge of the rib will project about .006 inch inwardly relatively to the foot of the rib where it joins the assembly edge.

In a corresponding manner the top side or edge of the locking recess or groove will point about .006 inch outwardly relatively to the bottom of the recess. This means that the necessary deformation to provide for the locking engagement is of the magnitude .0112 inch which surprisingly I have found is sufficient to secure a very safe locking engagement.

As indicated in FIGURE 5 the dimension of the lock rib perpendicular to the plane of assembly is slightly higher than the dimension of the lock groove so that when the parts are assembled a narrow slot 21 is left between the assembled edges of the casing parts in the interior of the casing. Hereby the elasticity of the plastic material used and the locking engagement between the inclined surfaces 18 and 20' will cause the two half parts of the casing to be drawn tightly together whereby a very tight exterior locking is secured. The difference in height, i.e., the dimension of the slot 21 may be of a magnitude between .005.006 inch.

As mentioned hereinbefore the plastic material selected for the manufacture of the casing parts must be characterized by a substantial stiffness and adequate elasticity. As an example of a suitable plastic material having these physical properties a styrene-acrylonitrile copolymer is mentioned as an example of commercially available plastic material which is suitable for the purpose, but it will be understood that any other suitable plastic materials having substantially similar physical properties can be used.

Since the elasticity depends on the wall structure and especially the edge zones, also the wall thickness must be selected in view of the plastic material used so as to enable the locking engagement by clicking the parts together without the danger of damaging the lock means. I found it convenient to select the wall thickness so that the pressure necessary to obtain the locking engagement is smaller when the casing is empty, i.e., without components positioned therein and in addition to dimension the components and/or their positioning members engaging with the inwardly extending ribs in such a manner that the elastic deformation of that one of the casing parts in which the components are mounted is limited by the stiffness of the components at one or more points along the length of the casing. For example, may the volume control member and the switch be selected of such dimensions that the elastic deformation of the easing portion 12 in transverse direction where these two components are located is limited to the necessary deformation of about .006 inch or even less. Thereby when the two casing parts are assembled these components will contribute to the safe locking engagement.

As mentioned the two parts of the casing can be assembled just by clicking them together which surprisingshells.

1y results in a very safe locking engagement which requires more force to disengage the parts once they are assembled.

In the dry cell compartment which is accessible through the aperture 38 no other components than the dry cell are located so that when the dry cell is removed the interior walls are accessible with exposed surfaces. Therefore, for the purpose of disassembling the casing structure the dry cell compartment can conveniently be used, for example by inserting a plier therein and spreading it out to engage it with the exposed interior walls whereby a dissembling of the casing can be etfectuated without the risk of damaging the casing.

Though in the foregoing the invention has been described in great detail with reference to FIGURES 15, it will be understood that the embodiments shown and described must be considered as an example only, and that modifications in various respects will be possible within the scope of the invention. As an example of a possible modification reference is made to FIGURE 6 which illustrates lock means in the form of lock projections 54 and 56 of the same configuration located adjacent the exterior and the interior side respectively of the two casing parts.

Such lock projections may be in the form of elongated ribs extending along a part of the length of the edges, or such lock projections may be distributed at suitable intervals along the edges. Also other modifications will be possible within the scope of the invention.

It will be appreciated that seen from another aspect the invention provides a plastic casing for a miniature hearing aid apparatus comprising two hollow shells of a relatively stiff elastic plastic material. The open sides of both shells are surrounded by a peripheral edge which may have one or more recesses such as exemplified by the recesses 30 and 38. When the shells are assembled these recesses define apertures communicating with the interior of the casing.

The assembly means is in the form of ribs integral with the shells extending along portions of the edges of said The ribs or rib portions of one shell form a smooth surface with the exterior surface of the respective shell and are designed as locking ribs on the inwardly facing side. The rib portions on the other shell the outwardly facing surfaces of which are designed as locking ribs for engagement with the inwardly facing surfaces of the ribs on the first part are also forming a smooth surface with the interior of the second shell in order to get the shell out of. the mould.

I claim:

1. In a miniature hearing aid apparatus in which miniature elements are arranged within a plastic casing, said casing comprising:

two shell parts provided with complementary edge portions facing each other and adapted to be assembled into said casing,

said edge portions being partially at least approximately linear and partially relatively strongly curved to form relatively sharper bends, and mutually interengageable locking means at said edge portions for holding the two parts together in the assembled condition of the casing and essentially consisting of only complementary under-cut means operable to elastically engage one with the other with said two shell parts assembled into said casing,

said complementary under-cut means being provided with cooperating inclined surfaces which abut against each other with said casing assembled,

said inclined surfaces forming an acute angle, which is less than 20 and larger than 3, with respect to a line perpendicular to the separating plane between said shell parts,

said angle being smaller within the regions of said bends than in the approximately linear regions of said edge portions.

2. In a miniature hearing aid apparatus in which miniature elements are arranged within a plastic casing, said casing comprising:

two shell parts provided with complementary edge portions facing each other and adapted to be assembled into said casing,

said edge portions being partially at least approximately linear and partially relatively strongly curved to form relatively sharper bends, and mutually interengageable locking means at said edge portions for holding the two parts together in the assembled condition of the casing and essentially consisting of only complementary under-cut means operable to elastically engage one with the other with said two shell parts assembled into said casing,

said complementary under-cut means being provided with cooperating inclined surfaces which abut against each other with said casing assembled,

said inclined surfaces forming an acute angle, which is less than 20 and larger than 3, with respect to a line perpendicular to the separating plane between said shell parts,

said angle being smaller within the regions of said bends than in the approximately linear regions of said edge portions,

said angle being of the order 7-10 within said approximately linear regions and being of the order of 35 within the regions of said bends.

3. In a miniature hearing aid apparatus in which miniature elements are arranged within a plastic casing, said casing comprising:

two shell parts provided with complementary edge portions facing each other and adapted to be assembled into said casing, said edge portions being partially at least approximately linear and partially relatively strongly curved to form relatively sharper bends,

and mutually interengageable locking means at said edge portions for holding the two parts together in the assembled condition of the casing and essentially consisting of only complementary under-cut means operable to elastically engage one with the other with said two shell parts assembled into said casing, whereby said casing is held together exclusively by said locking means, faces which abut against each other with said casing said complementary under-cut means being provided with substantially rectilinear cooperating inclined surassembled, the inclined surfaces at the outer undercut means sloping inwardly of said casing in the direction of the free extremity thereof, and the inclined surfaces at the inner under-cut means sloping outwardly of said casing in the direction of the free extremity thereof,

said inclined surfaces forming an acute angle, which is less than 20 and larger than 3", with respect to a line perpendicular to the separating plane between said shell parts,

said angle being smaller within the regions of said bends than in the approximately linear regions of said edge portions,

said angle being of the order 7-l0 within said approximately linear regions and being of the order of 35 within the regions of said bends,

the under-cut means provided with said outwardly inclined surfaces being somewhat higher than the depth of the complementary under-cut means provided with said inwardly inclined surfaces to provide a gap between the two parts.

4. In a miniature hearing aid apparatus in which miniature elements are arranged within a plastic casing, said casing comprising:

two shell parts provided with complementary edge portions facing each other and adapted to be assembled into said casing,

said edge portions being partially at least approximately linear and partially relatively strongly curved to form relatively sharper bends,

and mutually interengageable locking means at said edge portions for holding the two parts together in the assembled condition of the casing and essentially consisting of only complementary under-cut means operable to elastically engage one with the other with said two shell parts assembled into said casing, whereby said casing is held together exclusively by said locking means,

said complementary under-cut means being provided with substantially rectilinear cooperating inclined surfaces which abut against each other with said casing assembled, the inclined surfaces at the outer under-cut means sloping inwardly of said casing in the direction of the free extremity thereof, and the inclined surfaces at the inner under-cut means sloping outwardly of said casing in the direction of the free extremity thereof,

said inclined surfaces forming an acute angle, which is less than 20 and larger than 3, with respect to a line perpendicular to the separating plane between said shell parts,

said angle being smaller within the regions of said bends than in the approximately linear regions of said edge portions,

said angle being of the order 710 within said approximately linear regions and being of the order of 35 within the regions of said bends,

the under-cut means provided with said outwardly inclined surfaces being somewhat higher than the depth of the complementary under-cut means provided with said inwardly inclined surfaces to provide a gap between the two parts,

said shell parts being made of styrene-acrylonitrile copolymer.

5. In a miniature hearing aid apparatus in which miniature elements are arranged within a plastic casing, said casing comprising:

two shell. parts provided with complementary edge portions facing each other and adapted to be assembled into said casing,

and mutually interengageable locking means at said edge portions for holding the two parts together in the assembled condition of the casing and essentially consisting of only complementary under-cut means operable to elastically engage one with the other with said two shell parts assembled into said casing,

said complementary under-cut means being provided with cooperating inclined surfaces which abut against each other with said casing assembled,

said inclined surfaces forming an acute angle, which is less than 20 and larger than 3", with respect to a line perpendicular to the separating plane between said shell parts,

said angle being of the order of 7-10 within said approximately linear regions and being of the order of 3-5 within the regions of said bends.

6. In a'miniature hearing aid apparatus in which miniature elements are arranged within a plastic casing, said casing comprising:

two shell parts provided with complementary edge portions facing each other and adapted to be assembled into said casing,

and mutually interengageable locking means at said edge portions for holding the two parts together in the assembled condition of the casing and essentially consisting of only complementary under-cut means operable to elastically engage one with the other with said two shell parts assembled into said casing, whereby said casing is held together exclusively by said locking means,

said complementary under-cut means being provided with substantially rectilinear cooperating inclined sunrfaces which abut against each other with said casing assembled, the inclined surfaces at the outer under-cut means sloping inwardly of said casing in the direction of the free extremity thereof, and the inclined surfaces at the inner under-cut means sloping outwardly of said casing in the direction of the free extremity thereof,

said inclined surfaces forming an acute angle, which is less than 20 and larger than 3, with respect to a line perpendicular to the separating plane between said shell parts,

said angle being of the order 710 within said approximately linear regions and being of the order of 3-5 within the regions of said heads.

the under-cut means provided with said outwardly inclined surfaces being somewhat higher than the depth of the complementary under-cut means provided with said inwardly inclined surfaces to provide a gap between the two parts.

References Cited by the Examiner UNITED STATES PATENTS 2,597,087 5/1952 COWgill 117161 2,674,547 4/1954 Paxton et al. 117-161 2,720,332 10/1955 Holt 22060 2,959,645 11/ 1960 Ladd 2204 X 2,998,896 9/1961 Miller 2204 3,031,537 4/1962 Rose 179-107 3,035,127 5/1962 Strzalkowski 179107 3,095,995 7/ 1963 Foster 22060 FOREIGN PATENTS 1,114,848 10/1961 Germany.

THERON E. CONDON, Primary Examiner.

ROBERT H. ROSE, EARLE J. DRUMMOND,

Examiners.

H. W. GARNER, G. E. LOWRANCE,

Assistant Examiners. 

1. IN A MINIATURE HEARING AID APPARATUS IN WHICH MINIATURE ELEMENTS ARE ARRANGED WITHIN A PLASTIC CASING, SAID CASING COMPRISING: TWO SHELL PARTS PROVIDED WITH COMPLEMENTARY EDGES PORTIONS FACING EACH OTHER AND ADAPTED TO BE ASSEMBLED INTO SAID CASING, SAID EDGE PORTIONS BEING PARTIALLY AT LEAST APPROXIMATELY LINEAR AND PARTIALLY RELATIVELY STRONGLY CURVED TO FORM RELATIVELY SHARPER BENDS, AND MUTUALLY INTERENGAGEABLE LOCKING MEANS AT SAID EDGE PORTIONS FOR HOLDING THE TWO PARTS TOGETHER IN THE ASSEMBLED CONDITION OF THE CASING AND ESSENTIALLY CONSISTING OF ONLY COMPLEMENTARY UNDER-CUT MEANS OPERABLE TO ELASTICALLY ENGAGE ONE WITH THE OTHER WITH SAID TWO SHELL PARTS ASSEMBLED INTO SAID CASING, SAID COMPLEMENTARY UNDER-CUT MEANS BEING PROVIDED WITH COOPERATING INCLINED SURFACES WHICH ABUT AGAINST EACH OTHER WITH SAID CASING ASSEMBLED, SAID INCLINED SURFACES FORMING AN ACUTE ANGLE, WHICH IS LESS THAN 20* AND LARGER THAN 3*, WITH RESPECT TO A LINE PERPENDICULAR TO THE SEPARATING PLANE BETWEEN SAID SHELL PARTS, SAID ANGLE BEING SMALLER WITHIN THE REGIONS OF SAID BENDS THAN IN THE APPROXIMATELY LINEAR REGIONS OF SAID EDGE PORTIONS. 